1. Field of the Invention
The present invention relates to a laser light irradiation apparatus and in particular to a laser light irradiation apparatus for conducting a medical treatment such as heating, vaporization and incision of a living tissue by irradiating it with laser lights.
2. Description of Prior Art
Recently, the laser light treatment by irradiating an object tissue with laser lights for heating and/or vaporizing the tissue has been widely adopted. Such treatment relying on irradiation with the laser lights has an advantage in that damage to the tissue and bleeding is less.
A contact type laser probe is disclosed in U.S. Pat. No. 4,736,743 issued to the present inventor. With this laser probe, laser lights are emitted forward mainly from the front end of the probe.
In a body cavity such as stomach and blood vessel, it may be necessary to selectively irradiate the area in the cavity with the laser lights to prevent no irradiated area in the cavity from being thermally damaged with the laser lights.
In order to prevent such damage to the tissue, means for inserting a catheter into a blood vessel and for reflecting the laser lights at the head is provided in the U.S. Pat. No. 4,672,961.
If foreign material from tissue is deposited on the laser light reflecting surface when such type of laser light irradiation apparatus is used, the reflecting surface would be excessively heated on exposure to the laser lights and might be burnt. Accordingly, it is necessary to emit the laser lights at a low power. If the blood flows into the front end portion of the optical fiber or a foreign material is deposited thereon, the front end portion of the optical fiber might be excessively heated and the power of the emitted laser lights become insufficient.